The GTK3 theme many of you have asked about in our previous posts has been released: it's called Numix and it comes a flat, modern look with square corners, a dark panel and dark window theme with dark menus.

Numix is available for GTK 3.6 and it supports GNOME Shell, Unity, Pantheon, Xfce and Openbox.

For now, the theme is not available in a PPA but it should be pretty soon. Also, in the future, there will be some Numix variants (dark toolbar, etc.) along with a GNOME Shell and an icon theme.

Since it's compatible with GTK 3.6, the theme supports Ubuntu 12.10 and 13.04 (and obviously, other Linux distributions that ship with GTK 3.6). The theme probably works with GTK 3.4 (and thus Ubuntu 12.04), however, the inset shadows and text shadows won't work. However, please note that I didn't test it on GTK 3.4.

Numix GTK3 theme in GNOME Shell

Numix GTK3 theme in Unity

Update: the theme is now available in a PPA. To add the PPA and install it in Ubuntu, use the following commands:

For other Linux distributions or if you don't want to use the above PPA in Ubuntu, extract the downloaded archive and copy the extracted folder to /usr/share/themes. For instance, if you've extracted it in your home folder, run the following command to copy it to /usr/share/themes: